Milling a 0.040" thin wall

[Garreth50x]

I'm working on a part for a client and could use some advice. It's an electrode for a sinker EDM, milled from tellurium copper. The design has a very thin, tall feature, about 0.400" tall, and the finish I'm getting isn't great. Under the microscope, it looks pretty rough.. lots of chatter marks and uneven surfaces.

I need to get a better finish on this part as the burn tolerances are a bit tighter than usual. I was hoping to avoid having to hand-stone it, but the last attempt was a single-pass waterline cut with a 0.003" stepdown, and that took more than 10 minutes. The feature is so thin, only 0.040" thick, so I'm worried about trying a separate roughing and finishing pass.

What would be your go-to strategy for milling a feature like this to get a cleaner finish? I'm open to any suggestions on toolpaths, tooling, or machine settings. Thanks for all your help!!

 

[brunosars]

Use very light finish passes, minimal stepovers, climb milling, and a rigid setup

 

[SunnyD]

I'm working on a part for a client and could use some advice. It's an electrode for a sinker EDM, milled from tellurium copper. The design has a very thin, tall feature, about 0.400" tall, and the finish I'm getting isn't great. Under the microscope, it looks pretty rough.. lots of chatter marks and uneven surfaces.

I need to get a better finish on this part as the burn tolerances are a bit tighter than usual. I was hoping to avoid having to hand-stone it, but the last attempt was a single-pass waterline cut with a 0.003" stepdown, and that took more than 10 minutes. The feature is so thin, only 0.040" thick, so I'm worried about trying a separate roughing and finishing pass.

What would be your go-to strategy for milling a feature like this to get a cleaner finish? I'm open to any suggestions on toolpaths, tooling, or machine settings. Thanks for all your help!!

Garreth, to achieve a high quality surface finish and avoid hand stoning, the main challenge is managing chatter. I think the best strategy will be a separate roughing and finishing pass, focusing on tool rigidity and optimized, light cutting parameters for the final pass

 

[Alan]

For thin features like that, tool pressure becomes the enemy. Sometimes a high-speed toolpath with smaller stepdowns and a constant engagement angle helps reduce deflection. Some shops also take a spring pass after the final contour. Have you experimented with reducing coolant pressure or switching to mist just to cut vibration on that wall?